1. Field of the Invention
The present invention generally relates to a driver, and more particularly, to a driver of a field sequential display and a driving method thereof.
2. Description of Related Art
The backlight module of a conventional liquid crystal display (LCD) is usually designed with a white light source (usually emitted by a Cold cathode fluorescent lamp (CCFL)), and the white light source provides a backlight for each pixel through color filters. A red, a green, and a blue color filters are disposed above each pixel in the pixel array. Such a design increases the fabricating cost, and color mixing problem may be occurred between the red, green, and blue color filters. Besides, since color filters are disposed in a LCD, the light generated from the white light source is blocked by the color filters and accordingly the brightness of the LCD is reduced.
To resolve aforementioned problems, a color sequential display is developed based on a color sequential technique and a control circuit. In such a display, color fields are alternatively displayed. Accordingly, a color sequential display is also referred to as a field sequential display. In a field sequential display, light-emitting diodes (LEDs) of different colors are adopted to replace the conventional white light source, and the LEDs of different colors are alternatively lit at different time so that different colors can be displayed at different pixels. The theory of field sequential display is to rapidly alternate between red, blue and green images in succession within the time range of visual persistence of human eyes, so as to produce a color mixing effect and allow the human eyes to see full-color images.
Because the working principle of field sequential display is similar to that of super twisted nematic (STN) LCD, a field sequential display can display monochromatic images as a STN LCD if the LEDs of the field sequential display are not driven. Thus, when a field sequential display is in a color mode, the LEDs corresponding to one of the colors are sequentially lit so as to display color images, and when the field sequential display is in a monochrome mode, the LEDs thereof are turned off so that monochromatic images are displayed.
FIG. 1 illustrates a driving waveform of a conventional field sequential display in the color mode. Referring to FIG. 1, in the color mode, a frame period is divided into a red field, a green field, and a blue field display period, and the driving signals COM0˜COM31 respectively produce two pulses during the display period of each color field and are sent to scan lines in a display panel to drive the pixels of the display panel. Besides, corresponding LEDs are driven to display the corresponding color during the display period of each color field. FIG. 2 illustrates a driving waveform of a conventional field sequential display in the monochrome mode. Referring to FIG. 2, in the monochrome mode, the frame period is not divided, while the driving signals COM0˜COM31 respectively form two pulses during the frame period and are sent to scan lines of a display panel to drive the pixels of the display panel.
As described above, when the field sequential display is in the color mode, because the frame period is divided, the driving time of each scan line (i.e., the pulse period) is shorter. In order to prevent the effective driving time from being shortened, the pulse rising and falling time of the driving signals have to be reduced (i.e., the rising and falling rates have to be increased). Accordingly, a high current is necessary. Besides, in order to improve the display quality of the field sequential display, a high voltage has to be supplied in the field sequential display.
Contrarily, when the field sequential display is in the monochrome mode, because the frame period is not divided, the driving time of each scan line is longer than that in the color mode. Accordingly, the rising and falling time of the driving signals are longer than those in the color mode (means can adopt relatively low current in this model). Besides, in the monochrome mode, the display quality of the field sequential display is not that obvious and accordingly a relatively low voltage can be supplied in the field sequential display.
Generally speaking, only one power supply (or power device) is disposed in a field sequential display. Since a field sequential display is mostly in the color mode, the power supply is usually designed with a high voltage and a high current to meet the requirement of driving signals and displayed data in the color mode. Thus, when the field sequential display is in the monochrome mode, it is meaningless to generate the driving signals and displayed data by using a power with a high voltage and a high current, and power is consumed unnecessarily.